1. Field of the Invention
The present invention relates to the field of high-voltage bidirectional switches. The present invention more specifically relates to a bidirectional switch intended to be series-connected with a load, the assembly being supplied by a high A.C. voltage, for example, the mains.
2. Discussion of the Related Art
High-voltage switches for an A.C. load of the type to which the present invention relates are used, in particular, to control household appliances, for example, washing machines, in which one or several A.C.-supplied loads (motors, pumps, heating resistors, valves) must be controlled from the machine microcontroller.
A bidirectional switch capable of being controlled by a low-voltage signal may be formed of a triac, the gate of which receives a low-voltage control signal.
A triac must be turned on at each halfwave of the supply voltage since it turns off when the current between its two power terminals disappears.
Some switches comprise a triac control circuit which enables, when the triac is turned on by a control signal during a halfwave, maintaining it on until the end of the next halfwave.
A disadvantage of such switches is that the control circuit is generally complex and expensive to form. Further, such a circuit may require use of one or several high-voltage capacitors, which components are difficult to form and are relatively expensive.